Allowing customer to see time table of all staffs

if i have 2 staff one staff time shift is 8am-5pm and the second staff time slots are 11am-7pm and i dont allow the customer to select staff its random i want the time and date selection to show all slots eg 8am-7pm and then whichever the customer select it gets assigned to that staff. how can that be possible?

because in the current way it either shows 8am-5pm or 11am-7pm only separately on random. so if a customer is looking for slot 8am-9am and the system randomly select the second staff he will be shown 11am-7pm slots even though 8-9 a staff was available.